1. Field of the Invention
The present invention relates to a radio selective call receiver that is capable of receiving incoming calls and data over a plurality of service areas, and in particular, relates to a method of transferring the reception service area of the radio selective call receiver.
2. Description of the Related Art
In the current field of radio selective call receivers (pagers, pocket bells, etc.), service is provided in which a plurality of reception areas are registered and calls from neighboring areas are received while switching between reception areas.
Japanese Patent Laid-open No. 240952/95 and Japanese Patent Laid-open No. 162925/95 disclose examples of radio selective call receivers applied to this type of service.
The radio selective call receivers disclosed in these documents described above receive the frequency/area information of the reception area to which the radio selective call receiver is to be transferred from the present reception area in which synchronization is currently established, and the radio selective call receiver switches the receiving frequency based on the received frequency/area information.
As described above, a radio selective call receiver can therefore receive a transmitted message which is addressed to that radio selective call receiver when it has moved into the another reception area.
A transmitting station of the reception area in which a radio selective call receiver is currently established its synchronization inserts frequency information and area information relating to a new destination reception area in a call signal that is transmitted to the radio selective call receiver, and the radio selective call receiver can receive the new frequency information and area information that are transmitted from the transmitting station within the reception area.
As described above, each radio selective call receiver receives frequency and area information of the transfer destination transmitted from the transmitting station of a reception area in which synchronization is currently established and updates a frequency list, controls receiving frequency in accordance with this updated frequency list, and controls the operating power at a timing that corresponds to the transfer destination reception area.
In some cases, however, the frequency/area information of the transfer destination that is transmitted from a reception area in which synchronization is currently established is received incorrectly due to, for example, deterioration in the radio-wave conditions. Registering this type of unusable frequency/area information in the limited nonvolatile memory reduces the efficiency memory use.
In addition, successive attempts at detecting a reception area at a frequency calculated based on unusable frequency information (i.e., information that does not enable detection of a reception area) also entails a decrease in the efficiency of battery use.
It is an object of the present invention to provide a radio selective call receiver and method of transferring reception areas that allows transfer of reception areas only when the received frequency/area information of the transfer destination is legitimate and that can suppress unnecessary consumption of battery power.
To solve the above-described problems, the radio selective call receiver according to this invention is provided with: receiving means that can receive radio signals in a plurality of service areas each having a different assigned frequency; area information extracting means that extracts area information relating to a transfer destination service area from a radio signal of a first frequency that is currently being received; information listing means that allows adding and deleting of area information and assigned frequency information corresponding to each of the plurality of service areas; and timing means that provides a time limit for detection of the area information at a second frequency corresponding to the transfer destination service area.
The radio selective call receiver according to this invention is further provided with a control means that determines the second frequency that corresponds to area information relating to the transfer destination service area from among the assigned frequencies, adds to the information listing means the area information and second frequency relating to this transfer destination service area, and provisionally sets the receiving frequency of the radio signal by the receiving means to the second frequency.
In addition, the control means sets the second frequency as the first frequency in the radio selective call receiver if the area information is detected at the second frequency within the time limit.
If the control means of the radio selective call receiver cannot detect the area information at the second frequency within the time limit, the control means deletes the second frequency as well as the area information relating to the transfer destination service area that corresponds to this second frequency that were added to the information listing means.
In addition, the radio selective call receiver is provided with: holding means for temporarily holding area information relating to the transfer destination service area; and control means for determining the second frequency corresponding to area information relating to the transfer destination service area from among the assigned frequencies, holding in the holding means the second frequency and area information relating to the transfer destination service area, and provisionally setting the receiving frequency of radio signals by the receiving means to the second frequency.
If the control means of the radio selective call receiver detects the area information at the second frequency within the time limit, the control means adds this second frequency and the area information relating to the transfer destination service area that corresponds to this second frequency to the information listing means and sets this second frequency as the first frequency.
The radio selective call receiver is further provided with a synchronizing signal extracting means that extracts synchronizing signals from the radio signal, and the control means determines that the area information has been detected if synchronizing signals are extracted by the synchronizing signal extracting means.
The control means of the radio selective call receiver also determines that the signal has been detected if the area information contained in the radio signal matches any of the area information that is written in the information listing means.
According to the receiving method of transferring reception areas of the radio selective call receiver of the present invention, area information relating to a transfer destination service area is extracted from a radio signal of a first frequency that is currently being received; a second frequency corresponding to the area information is determined and the area information and second frequency are added to an information listing means; the second frequency is set as the first frequency if the area information is detected at the second frequency within a time limit; and the second frequency and the area information relating to the transfer destination service area that corresponds to this second frequency that were added to the information listing means are deleted if a area information cannot be detected at the second frequency within the time limit.
In addition, area information relating to a transfer destination service area is extracted from a radio signal of a first frequency that is currently being received; a second frequency corresponding to the area information is determined and the area information and second frequency are held in a holding means; and if the area information is detected at the second frequency within a time limit, the second frequency as well as the area information corresponding to this second frequency that are held in the holding means are added to the information listing means and further, the second frequency is set as the first frequency.
Finally, according to the method of transferring reception areas, a area information is determined to have been detected if synchronizing signals are extracted at the second frequency. A signal is also determined to have been detected if the area information contained in the radio signal matches any of the area information written in the information listing means.
The above and other objects, features, and advantages of the present invention will become apparent from the following description based on the accompanying drawings which illustrate examples of preferred embodiments of the present invention.